We present observations of the recently discovered comet-like main-belt object P/2010 R2 ( La Sagra ) obtained by Pan-STARRS 1 and the Faulkes Telescope-North on Haleakala in Hawaii , the University of Hawaii 2.2 m , Gemini-North , and Keck I telescopes on Mauna Kea , the Danish 1.54 m telescope ( operated by the MINDSTEp consortium ) at La Silla , and the Isaac Newton Telescope on La Palma .
An antisolar dust tail is observed to be present from August 2010 through February 2011 , while a dust trail aligned with the object ’ s orbit plane is also observed from December 2010 through August 2011 .
Assuming typical phase darkening behavior , P/La Sagra is seen to increase in brightness by > 1 mag between August 2010 and December 2010 , suggesting that dust production is ongoing over this period .
These results strongly suggest that the observed activity is cometary in nature ( i.e . , driven by the sublimation of volatile material ) , and that P/La Sagra is therefore the most recent main-belt comet to be discovered .
We find an approximate absolute magnitude for the nucleus of H _ { R } = 17.9 \pm 0.2 mag , corresponding to a nucleus radius of \sim 0.7 km , assuming an albedo of p = 0.05 .
Comparing the observed scattering surface areas of the dust coma to that of the nucleus when P/La Sagra was active , we find dust-to-nucleus area ratios of A _ { d } / A _ { N } = 30 - 60 , comparable to those computed for fellow main-belt comets 238P/Read and P/2008 R1 ( Garradd ) , and one to two orders of magnitude larger than for two other main-belt comets ( 133P/Elst-Pizarro and 176P/LINEAR ) .
Using optical spectroscopy to search for CN emission , we do not detect any conclusive evidence of sublimation products ( i.e. , gas emission ) , finding an upper limit CN production rate of Q _ { CN } < 6 \times 10 ^ { 23 } mol s ^ { -1 } , from which we infer an H _ { 2 } O production rate of Q _ { H _ { 2 } O } < 10 ^ { 26 } mol s ^ { -1 } .
Numerical simulations indicate that P/La Sagra is dynamically stable for > 100 Myr , suggesting that it is likely native to its current location and that its composition is likely representative of other objects in the same region of the main belt , though the relatively close proximity of the 13:6 mean-motion resonance with Jupiter and the ( 3 , -2 , -1 ) three-body mean-motion resonance with Jupiter and Saturn mean that dynamical instability on larger timescales can not be ruled out .